1. Field of the Invention
The present invention relates to processing of images displayed on a screen, particularly to technology for printing images.
2. Description of the Related Art
With advances in so-called digital technology, including computers, images are often handled as digital data (so-called image data). For example, today it is relatively easy to realize the conversion of pictures, photographs, documents, or the like to image data using a scanner, the generation of image data directly using a capture device such as a digital camera, and also the creation of image data on a computer. Since image data itself cannot be recognized as is as images, the image data is displayed on a monitor screen and the image is confirmed on the monitor screen. The image displayed by bright spots on the monitor screen is also printed on a printing medium using ink.
Here, when displaying an image on a monitor screen, rather than the image data being supplied as is to the monitor, it is supplied after suitable gradation conversion is performed. This is because of the following reasons. First, the dynamic range of the bright spots that can be output by the monitor screen does not necessarily have sufficient breadth for the range of gradations that can be used by the image data. Because of this, when the gradation range that can be used by the image data is compressed to a relatively narrow dynamic range of the monitor screen and displayed, the image has no contrast and is lacking in sharpness. Making effective use of the narrow dynamic range of the monitor screen, to display a more natural image, image data is supplied to the monitor after adding the following kinds of corrections. Specifically, the following corrections are implemented on image data.
(1) In the area from low gradations to medium gradations that have a relatively big effect on the visual quality of an image, the contrast of the image data is at least preserved, and if possible, strengthened.
(2) On the other hand, in the very low gradation area and the high gradation area that have little effect on the visual quality, the contrast of the image data is compressed.
By doing this, it is possible to match the overall image dynamic range to the range that can be displayed on the monitor screen without losing the visual quality of the image. This kind of gradation characteristics correction is performed as a part of the process called so-called gamma correction, and by changing the gamma value that is the correction parameter, it is possible to make various settings for the contrast compression level in the low gradation area and the high gradation area.
In this way, for the image data supplied to the monitor, the gradation characteristics are corrected as represented in the so-called gamma correction, and since the image data has the contrast adjusted, when printing an image displayed on a monitor screen, a prerequisite is to print an image for which the image data has the contrast adjusted in the same way. Also, when a plurality of monitors are connected to a host computer, and the gamma value set to each monitor is different, the contrast adjustment level is different according to which monitor the image is displayed on, so proposed is a technology which, by identifying the monitor on which the image is displayed and detecting the gamma value used with that monitor, adds a suitable gamma correction according to the monitor (see JP-A-7-79356).
However, despite the fact that printing was done using image data with the contrast shifted to be exactly the same as the image data displayed on the monitor screen, there was the problem that the actual printed image sometimes was an image that gave a different impression from the image displayed on the monitor screen.